Dialysis is a medical therapy that replaces the function of failing kidneys by filtering the blood to remove waste products, excess salts, and accumulated fluid. When kidney function drops significantly, dialysis is needed to manage these critical processes and maintain a stable internal environment. Managing blood pressure (BP) is a continuous challenge for patients with kidney failure, as sustained high or low BP significantly increases the risk of cardiovascular complications. Therefore, achieving and maintaining stable BP is a primary goal of effective dialysis treatment and long-term health management.
The Link Between Dialysis and Fluid Volume
The connection between dialysis and blood pressure stability centers on manipulating fluid volume through a process called ultrafiltration. During hemodialysis, excess fluid accumulated between treatments is pulled from the blood, mimicking the fluid-removing action of healthy kidneys. The volume removed is precisely calculated to bring the patient’s weight down to their “dry weight,” the lowest weight they can tolerate without developing low blood pressure symptoms. This rapid fluid removal decreases blood volume, directly impacting the circulatory system. The difference between pre-dialysis weight and dry weight determines the ultrafiltration rate, which is the greatest factor influencing BP stability during and immediately after treatment.
Causes and Management of Low Blood Pressure During Treatment
A significant drop in blood pressure during a dialysis session is known as Intradialytic Hypotension (IDH), and it is the most common complication affecting up to 25% of all treatments. IDH is typically defined as a decrease in BP accompanied by symptoms such as muscle cramps, dizziness, nausea, or yawning. The primary cause of IDH is an ultrafiltration rate that exceeds the body’s ability to refill the bloodstream from surrounding tissues. Other factors include using dialysate fluid that is too warm, which causes blood vessels to widen (vasodilation), or underlying cardiac dysfunction. Autonomic dysfunction, often associated with diabetes, can also impair the body’s ability to constrict blood vessels to maintain pressure during fluid removal.
Management of IDH requires immediate intervention by the clinical team to prevent organ injury from reduced blood flow. Interventions include slowing or temporarily stopping ultrafiltration to reduce volume loss. The patient may be placed in the Trendelenburg position (head lower than feet) to encourage blood flow to the brain, and intravenous fluid may be administered to rapidly restore circulating volume. Preventive strategies focus on minimizing fluid weight gain between sessions and using cooler dialysate to help maintain vascular tone.
Addressing High Blood Pressure Between Sessions
Chronic high blood pressure between dialysis sessions, known as Interdialytic Hypertension, is a long-term threat to cardiovascular health. The most common and treatable cause of persistent hypertension is hypervolemia, or excess fluid accumulation, often driven by dietary sodium intake. Sodium stimulates thirst, leading to greater fluid consumption between treatments. When the body retains excessive fluid and salt, the heart must pump harder, and hormonal systems such as the Renin-Angiotensin-Aldosterone System (RAAS) become overactive. This activation constricts blood vessels and raises blood pressure. Managing interdialytic hypertension requires meticulous control of fluid status through strict adherence to a low-sodium diet and limiting fluid intake.
For hypertension that persists despite achieving dry weight, medications are necessary to target non-volume-related mechanisms. Antihypertensive drugs, such as beta-blockers and certain calcium channel blockers, are frequently used to help lower blood pressure and protect the heart. The timing of medication intake is important, as taking BP medications just before a session can sometimes contribute to IDH, requiring careful adjustment by the healthcare team.
Accurate Monitoring and Target Goals
Accurate measurement of blood pressure is complicated in dialysis patients due to the wide BP fluctuations that occur around the treatment schedule. In-center measurements, particularly those taken immediately before or after a session, do not always reflect the patient’s average BP over the entire interdialytic period. Home blood pressure monitoring (HBPM) or ambulatory blood pressure monitoring (ABPM) provides a more reliable measure of the true blood pressure burden and is a better predictor of adverse outcomes.
When monitoring BP, patients must avoid using the arm with their vascular access (fistula or graft) to prevent damage to the site. Historically, targets for in-center readings have been suggested, such as a predialysis BP of less than 140/90 mm Hg and a postdialysis BP of less than 130/80 mm Hg. However, these goals are often individualized based on the patient’s age, symptoms, and the presence of other heart conditions. The most effective management involves consistent monitoring and open communication with the care team to ensure the treatment plan is tailored to the patient’s specific needs and tolerance.